Liquid crystal panel and polarizing laminate for use in the liquid crystal panel

ABSTRACT

A liquid crystal panel which is capable of significantly reducing a thickness thereof as compared to conventional liquid crystal panels, and, when used in a liquid crystal display device using a liquid crystal cell such as an IPS-type liquid crystal cell, reducing oblique light leakage in a black state of the liquid crystal display device to enhance contrast.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Divisional Application of U.S. patent applicationSer. No. 14/646,355, filed May 20, 2015, which claims the priority ofJapanese Patent Application No. 2013-227095, filed on Oct. 31, 2013, andJapanese Patent Application No. 2014-097503, filed on May 9, 2014, inthe JPO (Japan Patent Office), the disclosures of which are incorporatedherein in their entirety by reference. Further, this application is theNational Phase application of International Application No.PCT/JP2014/073160 filed on Sep. 3, 2014, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present invention relates to a liquid crystal panel. In particular,the present invention relates to a liquid crystal panel wherein a pairof polarizers are disposed, respectively, on opposite sides of a liquidcrystal cell containing liquid crystal molecules oriented or aligned inone direction in a plane of the cell under an electric field-off state,such as an IPS-type liquid crystal cell, and wherein a retardation layeris combined with one of the polarizers for viewing angle compensation.The present invention also relates to a laminate comprising a polarizerand a retardation layer for use in such a liquid crystal panel.

BACKGROUND ART

An IPS-type liquid crystal cell is configured to, under an electricfield-off state, achieve a homogeneous orientation or alignment ofliquid crystal molecules in which liquid crystal molecules are uniformlyoriented or aligned in one direction in a plane of the liquid crystalcell. In a liquid crystal display device equipped with such an IPS-typeliquid crystal cell having a structure as described above, a pair ofpolarizers are disposed, respectively, on opposite sides of the liquidcrystal cell in such a manner that absorption axes of the polarizersorthogonally intersect each other. Further, one of the polarizers isdisposed with respect to the liquid crystal cell such that theabsorption axis of the one polarizer is aligned in parallel to theorientation direction of the liquid crystal molecules in the electricfield-off state. Typically, this electric field-off state corresponds toa “black state”. On the other hand, a “white state” is achieved byapplying an electric field to the liquid crystal cell to rotate theliquid crystal molecules horizontally in the plane of the cell tothereby cause phase retardation of light through the liquid crystal cellin such a manner that the light which has passed through the onepolarizer is transmitted through the other polarizer. The “white state”is achieved when the liquid crystal molecules are oriented along axeseach bisecting an intersecting angle between the absorption axes of thepair of polarizers, or, in other words, the liquid crystal molecules areoriented at an orientation angle of 45° with respect to the absorptionaxes of the polarizers, to provide a maximum light transmittance. Inactual practice, however, it is difficult to have the liquid crystalmolecules rotated to the position of the ideal orientation angle of 45°,and therefore an orientation angle substantially equal to, or close to,45° is treated as being within the coverage of the “white state”. Aliquid crystal display device is called as “O-mode” if the polarizerlocated at an illumination source-side has its absorption axis parallelto the orientation direction of the liquid crystal molecules in theelectric field-off state, whereas, it is called as “E-mode” if thepolarizer at a viewing-side has its absorption axis parallel to theorientation direction of the liquid crystal molecules in the electricfield-off state.

In a liquid crystal display device equipped with the IPS-type liquidcrystal cell, problems have been experienced in that, when a userobserves a display screen at an angle of 45° with respect to theabsorption axis of the viewing side polarizers and obliquely withrespect to the plane of the liquid crystal cell, there is a decrease incontrast, and a change in display color is visually recognized whenobserved from different angles. In view of the problems, proposals havebeen made by, for example, the Patent Documents 1 and 2 which proposedisposing a plurality of retardation films on one side of the liquidcrystal cell to thereby solve the above problems. Further, as moreeffective solution than the proposals by the Patent Documents 1 and 2,the Patent Document 3 proposes to use two retardation films consistingof a “negative biaxial plate” and a “positive biaxial plate”, incombination with the one polarizer. According to this proposal, thenegative biaxial plate is defined as an optical component having arelationship of nx1>ny1>nz1, where nx1 represents a refractive index ina slow axis (x-axis) direction, ny1 represents a refractive index in afast axis (y-axis) direction, and nz1 represents a refractive index in athickness-wise (z-axis) direction, whereas the positive biaxial plate isdefined as an optical component having a relationship of nz2>nx2>ny2,where nx2 represents a refractive index in the slow axis (x-axis)direction, ny2 represents a refractive index in the fast axis (y-axis)direction, and nz2 represents a refractive index in the thickness-wise(z-axis) direction. Further, in the Patent Document 3, in-plane andthickness-wise retardation values of the negative and positive biaxialplates, and mutual relationships of the retardation values, arespecified in detail. According to the teachings of the Patent Document3, the arrangement proposed by this Document makes it possible to reducelight leakage in the oblique direction in a black state of a liquidcrystal display device to enhance contract.

CITATION LIST Parent Document

Parent Document 1: JP 11-133408A

Parent Document 2: JP 2006-178401A

Parent Document 3: JP 4938632B

Parent Document 4: JP 4751481B

Parent Document 5: JP 4751486B

Parent Document 6: JP 5244848B

SUMMARY OF INVENTION Technical Problem to be Solved by the Invention

A recent key issue in liquid crystal display devices is a reduction inthickness thereof. Particularly, in a liquid crystal display deviceformed by having a polyvinyl alcohol-based layer impregnated with iodineso that the iodine is adsorbed to the polyvinyl alcohol-based layer,dimensional changes such as expansion and contraction occur in thepolyvinyl alcohol-based layer under environmental conditions such assurrounding temperature and humidity, to such an extent that a stressdue to the dimensional changes gives rise to a distortion in an adjacentoptical film, causing deterioration in image quality. There is also astrong need to reduce a thickness of the entire device. The techniqueproposed in the Patent Document 3 may be effective, in a liquid crystaldisplay device using a liquid crystal cell containing liquid crystalmolecules oriented in one direction in a plane of the liquid crystalcell in an electric field-off state, such as an IPS-type liquid crystalcell, for reducing oblique light leakage in a black state of the liquidcrystal display device to enhance contrast. However, a reduction inthickness of each layer is not taken into consideration at all.

In view of such circumstances, the present invention addresses atechnical problem of providing a liquid crystal panel capable ofsignificantly reducing an overall thickness thereof as compared toconventional liquid crystal panels, and, when used in a liquid crystaldisplay device having a liquid crystal cell containing liquid crystalmolecules oriented in one direction in a plane thereof in an electricfield-off state, such as an IPS-type liquid crystal cell, reducingoblique light leakage in a black state of the liquid crystal displaydevice to enhance contrast.

The present invention also addresses another technical problem ofproviding a laminate comprising a polarizer and a retardation layer, andsuitably usable in a liquid crystal display device using a liquidcrystal cell containing liquid crystal molecules oriented in onedirection in a plane thereof in an electric field-off state, such as anIPS-type liquid crystal cell.

Solution to Technical Problem

According to one aspect of the present invention, there is provided aliquid crystal panel which comprises a liquid crystal cell having aliquid crystal layer containing liquid crystal molecules oriented in onedirection in a plane thereof in an electric field-off state, such as anIPS-type liquid crystal cell. A first polarizer is disposed on one ofopposite sides of the liquid crystal cell, and a second polarizer isdisposed on the other side of the liquid crystal cell. The first andsecond polarizers are arranged in such a manner that absorption axesthereof orthogonally intersects each other. A first retardation layerand a second retardation layer are provided between the first polarizerand the liquid crystal cell and arranged in this order from the side ofthe first polarizer, wherein the first retardation layer is configuredto satisfy the relationship of nx1>ny1>nz1, where nx1 represents arefractive index in an in-plane slow axis (x-axis) direction, ny1represents a refractive index in an in-plane fast axis (y-axis)direction, and nz1 represents a refractive index in a thickness-wise(z-axis) direction, and the second retardation layer is configured tosatisfy the relationship of nz2>nx2>ny2, where: nx2 represents arefractive index in the in-plane slow axis (x-axis) direction, ny2represents a refractive index in the in-plane fast axis (y-axis)direction, and nz2 represents a refractive index in the thickness(z-axis) direction. Further, the slow axis of the first retardationlayer is disposed parallel to the slow axis of the second retardationlayer.

In the liquid crystal panel of the present invention, each of the firstpolarizer and the second polarizer has a thickness of 10 μm or less, andexhibits optical properties having a single transmittance of 40.0% ormore and a polarization degree of 99.8% or more.

The second polarizer is directly bonded to the liquid crystal cellthrough a pressure-sensitive adhesive layer in such a manner that theabsorption axis thereof is disposed approximately parallel to anorientation direction of the liquid crystal molecules of the liquidcrystal cell in the electric field-off state.

Further, the second polarizer is provided with a protective layerlaminated to a surface thereof on a side opposite to the liquid crystalcell, through a pressure-sensitive adhesive layer, wherein theprotective layer has a thickness of 10 to 50 μm, and exhibits a moisturepermeability of 200 g/m² or less.

The first retardation layer has a thickness of 25 μm or less,preferably, 3 to 25 μm as presented in Table 1, and exhibits a moisturepermeability of 200 g/m² or less, wherein a value of Δnxy1 and a valueof Δnxz1 are set, respectively, to 0.0036 or more, preferably, 0.0036 to0.014 as represented in Table 1, and 0.0041 or more, preferably, 0.0041to 0.0238 as represented in Table 1, and Re and Rth are set,respectively, in the range of 90 nm to 140 nm and the range of 100 nm to240 nm, where: Δnxy1 represents an in-plane refractive index differencewhich is a difference between the refractive index nx1 in the slow axisdirection and the refractive index ny1 in the fast axis direction; Δnxz1represents a thicknesswise refractive index difference which is adifference between the refractive index nx1 in the slow axis directionand the refractive index nz1 in the thickness (z-axis) direction; Rerepresents an in-plane retardation; and Rth represents a thicknesswiseretardation expressed in the following formula: Rth=(nx1−nz1)×d1, whered1 represents a thickness of the first retardation layer.

The second retardation layer has a thickness of 20 μm or less,preferably, 1 to 20 μm as presented in Table 1, wherein a value of ×nxy2and a value of Δnxz2 are set, respectively, to 0.0008 or more,preferably, 0.0008 to 0.010 as presented in Table 1, and −0.0030 orless, preferably, −0.0220 to −0.0030 as presented in Table 1, and Re andRth are set, respectively, in the range of 15 nm to 50 nm and the rangeof −110 nm to −60 nm, where: Δnxy2 represents a difference between therefractive index nx2 in the slow axis direction and the refractive indexny2 in the fast axis direction; Δnxz2 represents a difference betweenthe refractive index nx2 in the slow axis direction and the refractiveindex nz2 in the thickness (z-axis) direction; Re represents an in-planeretardation; and Rth represents a thicknesswise retardation expressed inthe following formula: Rth=(nx2−nz2)×d2, where d2 represents a thicknessof the second retardation layer.

TABLE 1 Thickness In-plane retardation Thicknesswise retardation Firstretardation layer 3 μm ≦ d ≦ 25 μm 0.0036 ≦ Δnxy ≦ 0.014   0.0041 ≦ Δnxz≦ 0.0238 (nx > ny > nz) Second retardation layer 1 μm ≦ d ≦ 20 μm 0.0008≦ Δnxy ≦ 0.010 −0.0220 ≦ Δnxz ≦ − 0.0030 (nz > nx > ny)

Further, the first polarizer is provided with a protective layerlaminated to a surface thereof on a side opposite to the firstretardation layer, wherein the protective layer has a thickness of 50 μmor less, and exhibits a moisture permeability of 200 g/m² or less.

In the first aspect of the present invention, a thickness of a laminatecomprising the first polarizer, the first and second retardation layersand the protective layer provided on the first polarizer is 105 μm plusa thickness of a pressure-sensitive adhesive layer, at a maximum, in apreferred embodiment, about 90 μm plus a thickness of apressure-sensitive adhesive layer. Thus, the liquid crystal panel of thepresent invention is significantly reduced in thickness as compared toconventional liquid crystal panels.

A polarizer having a thickness of 10 μm or less and exhibiting the aboveoptical properties represented by a single transmittance and apolarization degree can be produced by a method described in any one ofthe Patent Documents 4, 5 and 6 proposed by the applicant of thisapplication.

In the aforementioned aspect of the present invention, the in-planerefractive index difference Δnxy of the first retardation layer is0.0036 or more, and the thicknesswise refractive index difference Δnxzof the first retardation layer is 0.0041 or more. By determining therefractive index differences in this manner, it becomes possible toachieve a reduction in thickness of the first retardation layer whilerealizing values of the in-plane retardation Re and the thicknesswiseretardation Rth necessary for optical compensation.

The in-plane refractive index difference Δnxy of the second retardationlayer is 0.0008 or more, and the thicknesswise refractive indexdifference Δnxz of the second retardation layer is −0.0030 or less. Bysetting the refractive index differences in this manner, it becomespossible to achieve a reduction in thickness of the second retardationlayer while realizing values of the in-plane retardation Re and thethicknesswise retardation Rth necessary for optical compensation.

Both of the first and second polarizers have a thickness of 10 μm orless. By determining the thickness of the polarizer to 10 μm or less, itbecomes possible to suppress an influence of a stress due to expansionand contraction occurring in the polarizer along with surroundingenvironmental changes, on an adjacent layer. In the case where apolarizer has a relatively large thickness, for example, of 25 to 30 μm,as in conventional liquid crystal panels, relatively large expansion andcontraction forces are produced in the polarizer, so that it becomesnecessary to laminate a protective layer or a retardation layer having athickness enough to suppress the expansion and contraction of thepolarizer. In the first aspect of the present invention, each of thepolarizers is thinned to reduce expansion and contraction forces whichcan be produced in the polarizer, so that it becomes possible to reducea thickness of the protective layer or the retardation layer to belaminated to the polarizer.

The moisture permeability of the protective layer is 200 g/m² or less. Apolarizer has a problem that a reduction in thickness thereof causesdeterioration in humidity resistance. Thus, the moisture permeability ofthe protective layer is set to a relatively small value as above. Thismakes it possible to suppress degradation of the polarizer due tohumidity to thereby allow the polarizer to be reduced in thickness.

In the aforementioned aspect of the present invention, the moisturepermeability of the first retardation layer located on a near side withrespect to the first polarizer is 200 g/m² or less. By setting themoisture permeability of the first retardation layer to a relativelysmall value as above, it becomes possible to suppress degradation of thepolarizer due to humidity to thereby allow the polarizer to be reducedin thickness, as with the aforementioned case of the protective layer.

In the case where the protective layer is disposed on a viewing side ofa liquid crystal display device, one or both of an anti-glare layer andan anti-reflection layer may be provided on an outer surface thereof.

According to a second aspect of the present invention, there is provideda laminate of polarizer and retardation layers. The laminate is designedfor use, in a liquid crystal panel which comprises a liquid crystal cellhaving a liquid crystal layer containing liquid crystal moleculesoriented in one direction in a plane thereof in an electric field-offstate, and a pair of polarizers disposed, respectively, on oppositesides of the liquid crystal cell in such a manner that absorption axesthereof orthogonally intersect each other, wherein the laminate islocated between the liquid crystal cell and one of the polarizers.

The laminate includes a first retardation layer disposed adjacent to theone polarizer, and a second retardation layer laminated to the firstretardation layer. The first retardation layer is configured to satisfythe relationship of nx1>ny1>nz1, where nx1 represents a refractive indexin an in-plane slow axis (x-axis) direction, ny1 represents a refractiveindex in an in-plane fast axis (y-axis) direction, and nz1 represents arefractive index in a thickness-wise (z-axis) direction, whereas thesecond retardation layer is configured to satisfy the relationship ofnz2>nx2>ny2, where nx2 represents a refractive index in the in-planeslow axis (x-axis) direction, ny2 represents a refractive index in thein-plane fast axis (y-axis) direction, and nz2 represents a refractiveindex in the thickness-wise (z-axis) direction, wherein the slow axis ofthe first retardation layer is disposed parallel to the slow axis of thesecond retardation layer.

The first retardation layer has a thickness of 25 μm or less,preferably, 3 to 25 μm, and exhibits a moisture permeability of 200 g/m²or less, wherein the value of Δnxy1 and the value of Δnxz1 aredetermined, respectively, to 0.0036 or more, preferably, 0.0036 to0.014, and 0.0041 or more, preferably, 0.0041 to 0.0238, and Re and Rthare determined, respectively, in the range of 90 nm to 140 nm and therange of 100 nm to 240 nm, where Δnxy1 represents an in-plane refractiveindex difference in terms of a difference between the refractive indexnx1 in the slow axis direction and the refractive index ny1 in the fastaxis direction, Δnxz1 represents a thicknesswise refractive indexdifference in terms of a difference between the refractive index nx1 inthe slow axis direction and the refractive index nz1 in thethickness-wise (z-axis) direction, Re represents an in-planeretardation, and Rth represents a thicknesswise retardation expressed inthe formula Rth=(nx1−nz1)×d1, where d1 represents the thickness of thefirst retardation layer.

The second retardation layer has a thickness of 20 μm or less,preferably, 1 to 20 μm, wherein the value of ×nxy2 and the value ofΔnxz2 are determined, respectively, to 0.0008 or more, preferably,0.0008 to 0.010, and −0.0030 or less, and Re and Rth are determined,respectively, in the range of 15 nm to 50 nm and the range of −110 nm to−60 nm, where ×nxy2 represents an in-plane refractive index differencein terms of a difference between the refractive index nx2 in the slowaxis direction and the refractive index ny2 in the fast axis direction,Δnxz2 represents a thicknesswise refractive index difference in terms ofa difference between the refractive index nx2 in the slow axis directionand the refractive index nz2 in the thickness-wise (z-axis) direction,Re represents an in-plane retardation, and Rth represents athicknesswise retardation expressed in the formula Rth=(nx2−nz2)×d2,where d2 represents the thickness of the second retardation layer.

Further, the slow axis of the first retardation layer is disposedparallel to the slow axis of the second retardation layer.

Generally, a polarizer is prepared by having a polyvinyl alcohol(PVA)-based layer impregnated with a dichroic material such that thedichroic material is adsorbed to the PVA-based layer, through a dyeingstep, and uniaxially or biaxially stretching the PVA-based resin film tohave the adsorbed dichroic material oriented in the stretch direction.In recent years, iodine has been commonly used as the dichroic material.In the dyeing step, the PVA-based resin film is immersed in an aqueousiodine solution. In this regard, however, iodine molecules (I₂) are notsoluble in water by themselves. for the purpose, iodine is dissolved inwater together with potassium iodide (KI) to prepare an aqueousiodine-potassium iodide solution. In the aqueous iodine-potassium iodidesolution, in addition to potassium ions (K⁺) and iodine ions (I⁻), thereexist polyiodide ions (I₃ ⁻ and I₅ ⁻) formed by coupling between iodineions and an iodine molecule. In the dyeing step, iodine ions andpolyiodide ions penetrate into the PVA-based resin film and are adsorbedonto the molecules of the PVA-based resin. Then, in the subsequentstretching step, when the PVA-based resin film is stretched and themolecules are oriented, the polyiodide ions are also oriented in astretching direction. The transmittance of light entering into the dyedand stretched PVA-based resin varies depending on the angle ofpolarization direction of the entering light with respect to theorientation direction of the oriented polyiodide ions, so that the dyedand stretched PVA-based resin functions as a polarizer.

As above, polarizers comprise at least a PVA-based resin and polyiodideions. In the polarizer, the polyiodide ions are present in a state inwhich they form PVA-iodine complexes (PVA·I₃ ⁻ and PVA·I₅ ⁻) by aninteraction with the PVA-based resin. By forming such a complexes, anabsorption dichroism is exhibited in a wavelength range of visiblelight. An iodine ion (I⁺) has an absorption peak around 230 nm. Atriiodide ion in a complexed state with PVA (PVA·I₃ ⁻) has an absorptionpeak around 470 nm. A pentaiodide ion in a complexed state with PVA(PVA·I₅ ⁻) has an absorption peak around 600 nm. A wavelength of lightto be absorbed varies depending on a type of PVA-iodine complex, so thatthe polyiodide ion has a broad absorption peak. PVA-iodine complexesabsorb visible light. On the other hand, an iodine ion has a peak around230 nm, i.e., does not absorb visible light. Thus, the amount ofpolyiodide ions complexed with PVA exerts an influence on theperformance of a polarizer in a display device such as a liquid crystaldisplay device.

In the present invention, the thickness of each of the polarizers is 10μm or less, preferably, 8 μm or less, particularly preferably, 6 μm orless. By having such thin thickness of the polarizer, it becomespossible to reduce expansion and contraction forces which can beproduced in the polarizer along with surrounding environmental changes.In the case where a polarizer has a relatively large thickness,relatively large expansion and contraction forces are produced in thepolarizer, so that it becomes necessary to laminate a protective layeror a retardation layer having a thickness enough to suppress expansionand contraction of the polarizer. In contrast, by having such a thinthickness of each of the polarizers to reduce expansion and contractionforces which can be produced in the polarizer, it becomes possible toreduce the thickness of the protective layer or the retardation layer tobe laminated to the polarizer, and reduce an overall thickness of theoptical laminate. In addition, as a result of reducing the thickness ofthe polarizer to reduce expansion and contraction forces which can beproduced in the polarizer along with surrounding environmental changes,it becomes possible to obtain an advantage of reducing a stress actingon a member laminated to the polarizer to suppress an optical distortionwhich can occur in the laminated member.

Preferably, each of the polarizers exhibits an absorption dichroism atany wavelength in a wavelength range of 380 nm to 780 nm. The singletransmittance of the polarizer is preferably 40.0% or more, morepreferably, 40.5% or more, further preferably, 41.0% or more,particularly preferably 41.5% or more. The polarization degree of thepolarizer is preferably 99.8% or more, more preferably, 99.9% or more,further preferably, 99.95% or more. It is not easy to produce such athinned polarizer exhibiting high polarization performance. However, athinned polarizer with desired properties can be produced by employing amethod described in any one of the Patent Documents 4, 5 and 6 proposedby the applicant of this application.

As the protective layer, any suitable resin film may be employed as longas it can satisfy the following moisture permeability requirement underthe following thickness condition. Examples of a material suitablyusable in the present invention to form the protective layer include: acycloolefin-based resin such as a norbornene-based resin; anolefin-based resin such as polyethylene or polypropylene; apolyester-based resin; and a (meth) acrylic-based resin. It should benoted that the term “(meth) acrylic-based resin” herein means anacrylic-based resin and/or a methacrylic-based resin.

The thickness of the protective layer is 50 μm or less, typically, 10 μmto 50 μm, preferably, 15 μm to 45 μm. In the case where the protectivelayer is disposed on a viewing side of a liquid crystal display device,a surface treatment layer such as an anti-glare layer or ananti-reflection layer may be provided, as mentioned above.

The moisture permeability of the protective layer is 200 g/m² or less,preferably, 170 g/m² or less, more preferably, 130 g/m² or less,particularly preferably, 90 g/m² or less. Each of the polarizers used inthe present invention has a thickness of 10 μm or less. Generally, apolarizer has a problem that a reduction in thickness thereof causesdeterioration in humidity resistance. Thus, the moisture permeability ofthe protective layer is set to a relatively small value as above. Thismakes it possible to suppress degradation of the polarizer due tohumidity to thereby allow the polarizer to be reduced in thickness. Byallowing the polarizer to be reduced in thickness, the thickness of theprotective layer or the retardation layer to be laminated to thispolarizer can also be reduced, as mentioned above, so that it becomespossible to reduce an overall thickness of the optical laminate.

A material usable for the first retardation layer must be capable ofsatisfying the above moisture permeability requirement. Examples of theusable material may include: a polycarbonate-based resin; apolyester-based resin such as polyethylene terephthalate or polyethylenenaphthalate; a polyarylate-based resin; a polyimide-based resin; acyclic polyolefin-based (polynorbornene-based) resin; a polyamide resin;and a polyolefin-based resin such as polyethylene or polypropylene.

Examples of a preferred material usable for the second retardation layermay include an acrylic-based resin, a styrene-based resin, amaleimide-based resin and a fumarate-based resin. However, the usablematerial is not particularly limited, but may be any polymer materialhaving a negative birefringence. The term “having a negativebirefringence” means a property that, when a polymer is oriented bymeans of stretching or the like, a refractive index in an orientationdirection thereof becomes relatively small, in other words, a refractiveindex in a direction perpendicular to the orientation direction becomesrelatively large. Examples of such a polymer include a polymer in whicha chemical bond or a functional group having large polarizationanisotropy, such as an aromatic group or a carbonyl group, is introducedinto a side chain thereof.

Meritorious Effects of the Invention

As mentioned above, according to the present invention, each of thepolarizer, and the retardation layer and the protective layer laminatedto the polarizer, can be configured to be thin, so that it becomespossible to significantly reduce the overall thickness of the liquidcrystal panel as compared to conventional liquid crystal panels. Inaddition, by having each of the refractive indexes of the first andsecond retardation layers laminated to the first polarizer within aspecific range, it becomes possible to significantly reduce thethickness while achieving an intended optical compensation effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a fragmentally cross-sectional view illustrating a liquidcrystal panel according to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

FIG. 1 is a sectional view illustrating a liquid crystal panel accordingto one embodiment of the present invention. In this FIGURE, the liquidcrystal panel 1 comprises an IPS-type liquid crystal cell 10. A firstpolarizer 11 and a second polarizer 21 are disposed, respectively, onthe opposite sides of the liquid crystal cell 10. A first retardationlayer 12 and a second retardation layer 13 are disposed between thefirst polarizer 11 and the liquid crystal cell 10, and arranged in thisorder from the side of the first polarizer 11.

Each of the first polarizer 11 and the second polarizer 21 is a typeobtained by impregnating a stretched polyvinyl alcohol-based resin layerwith iodine, wherein each of them has a thickness of 10 μm or less,typically, 5 μm. As the first polarizer 11, a type exhibiting opticalproperties including a single transmittance of 40.8% and a polarizationdegree of 99.99% or more is typically used. As the second polarizer 21,a type exhibiting optical properties including a single transmittance of42.8% and a polarization degree of 99.95% or more is typically used.

The first retardation layer 12 may be formed using any one of thematerials presented as examples suitable for the first retardationlayer-forming material. It has a thickness, typically, of 25 μm. Thefirst retardation layer 12 is configured to satisfy optical propertiesincluding the aforementioned moisture permeability and refractive index,and bonded to a surface of the first polarizer 11.

The second retardation layer 13 may be formed using any one of thematerials presented as examples suitable for the second retardationlayer-forming material. It has a thickness, typically, of 20 μm. Thesecond retardation layer 13 is configured to satisfy optical propertiesincluding the aforementioned refractive index, and bonded to a surfaceof the first retardation layer 12 on a side opposite to the firstpolarizer 11 through a pressure-sensitive adhesive layer or adhesivelayer 14. Further, the second retardation layer 13 is bonded to one ofopposite surfaces of the liquid crystal cell 10 through apressure-sensitive adhesive layer or adhesive layer 15.

For reducing the thickness of the laminate including the polarizer, itis preferable that each of the first retardation layer 12 and the secondretardation layer 13 is laminated to the liquid crystal cell through anadhesive layer using a light-curable adhesive. In this case, preferably,the adhesive layer has a storage elastic modulus of 3×10⁵ to 1×10⁸ Pa(25° C.). If the storage elastic modulus is less than 3×10⁵ Pa (25° C.),peeling is likely to occur due to poor adhesive force. On the otherhand, if the storage elastic modulus is greater than 1×10⁸ Pa (25° C.),peeling is likely to occur due to poor shock resistance.

The adhesive layer has a thickness, preferably, of 0.1 μm to 5.0 μm,more preferably, of 0.2 μm to 2.0 μm. If the thickness is less than 0.1μm, peeling is likely to occur due to poor shock resistance.

The adhesive layer has a peel force (90°), preferably, of 0.5 N/15 mmwidth or more, more preferably, of 1.0 N/15 mm width or more. If thepeel force is less than 0.5 N/15 mm width, peeling of the adhesive layeris likely to occur when a surface protective layer is peeled.

As a light-curable adhesive, it is possible to use a type obtained byirradiating with an activation energy ray a composition containing aradical polymerizable compound or an optical radical polymerizationinitiator, substantially without containing any organic solvent, andhaving a liquid viscosity of 1 to 100 cp/25° C.

As the radical polymerizable compound, it is possible to use a compoundcontaining an N-vinyl compound and an acrylamide derivative, a (meth)acrylate compound having one (meth) acryloyl group, a (meth) acrylatecompound having two or more (meth) acryloyl groups, or the like.

As the optical radical polymerization initiator, it is possible to usean initiator containing a thioxanthone-based initiator.

The above composition may further contain a silane coupling agent havingat least one organic group selected from the group consisting of anamino group, an acid anhydride, an epoxy group, a triazine ring and a(meth) acryloyl group.

A protective layer 16 is bonded to a surface of the first polarizer 11on a side opposite to the first retardation layer 12. The protectivelayer 16 has a thickness of 40 μm, and exhibits a moisture permeability,typically, of 80 g/m². An anti-reflection layer 17 is provided on anouter surface of the protective layer 16. The anti-reflection layer 17has a thickness of 7 μm. Specifically, as the protective layer 16 withthe anti-reflection layer 17, an acrylic-based protective film withanti-reflection function (DSG 11 produced by Dai Nippon Printing Co.,Ltd., thickness: 47 μm) may be used. Instead of or in addition to theanti-reflection layer 17, an optical film such as a brightness-enhancingfilm may be used.

The second polarizer 21 is bonded to the other surface of the liquidcrystal cell 10 through a pressure-sensitive adhesive layer 22. Aprotective layer 23 is bonded to a surface of the second polarizer 21 ona side opposite to the liquid crystal cell 10. The protective layer 23may have the same configuration as that of the protective layer 16. Abrightness-enhancing film 25 is bonded to an outer surface of theprotective layer 23 through a pressure-sensitive adhesive layer 24.

When the liquid crystal panel having the above configuration is used inthe O-mode, a side of the brightness-enhancing film 25 is positioned ona light source side, and a side of the anti-reflection layer 17 ispositioned on a viewing side. On the other hand, when used in theE-mode, the side of the brightness-enhancing film 25 is positioned onthe viewing side, and the side of the anti-reflection layer 17 ispositioned on the light source side.

EXAMPLES

An example of production of a liquid crystal panel according to thepresent invention and an evaluation method for the liquid crystal willbe described below.

[Measurement of Transmittance and Polarization Degree of Polarizer]

A single transmittance T, a parallel transmittance Tp and a crossedtransmittance Tc of a polarizer was measured using a UV-visiblespectrophotometer (V7100 produced by JASCO Corporation). As usedtherein, the term “parallel transmittance” means a transmittancemeasured when two polarizers having the same configuration are laminatedto allow absorption axes thereof to become parallel to each other, andthe term “crossed transmittance” means a transmittance measured when thetwo polarizers having the same configuration are laminated to allow theabsorption axes thereof to orthogonally intersect each other. On theother hand, the term “single transmittance” means a transmittance of asingle polarizer. Each value of T, Tp and Tc is a Y value measured bythe 2-degree visual field (C light source) of JIS Z8701 and correctedfor spectral luminous efficacy. The measurement was performed in a statein which a protective layer (acrylic-based resin film orcycloolefin-based resin film) was laminated to the polarizer in order tofacilitate handling of the polarizer. Light absorption of the protectivelayer is negligibly small as compared to light absorption of thepolarizer. Thus, a transmittance of a laminate obtained by laminatingthe protective layer to the polarizer was determined as a transmittanceof the polarizer.

The polarization degree P is derived from the following formula by usingthe above parallel transmittance and crossed transmittance.

Polarization degree P={(Tp−Tc)/(Tp+Tc)}^(1/2)×100

[Measurement of Thickness]

A thickness of each of the polarizer and the protective layer wasmeasured using a digital micrometer (KC-351C produced by AnritsuCorporation).

[Measurement of Moisture Permeability]

Moisture permeability was measured based on the moisture permeabilitytest method for moisture-proof packaging material (cup method) describedin JIS Z 0208.

[Production of First Polarizer]

An amorphous-polyethylene terephthalate (A-PET) film (produced byMitsubishi Plastics, Inc., trade name: NOVACLEAR SH046, thickness: 200μm) was preliminarily prepared as a substrate, and a surface thereof wassubjected to a corona treatment (58 W/m²/min). Further, PVA(polymerization degree: 4,200, saponification degree: 99.2%) added with1 wt % of an acetoacetyl-modified PVA (produced by The Nippon SyntheticChemical Industry Co., Ltd., trade name “GOHSEFIMER Z200”(polymerization degree: 1,200, saponification degree: 99.0% or more,acetoacetyl modification degree: 4.6%)) was preliminarily prepared, andapplied to the corona-treated surface of the substrate to form a filmthereon in such a manner as to allow the film to have a thickness of 12μm after drying. Then, the film was dried by hot air in an atmosphere at60° C. for 10 minutes to prepare a laminate of the substrate and aPVA-based resin layer provided on the substrate.

Subsequently, the laminate was stretched in air at 130° C., at astretching ratio of 2.0 times, to form a stretched laminate. Then, astep of immersing the stretched laminate in an insolubilizing aqueousboric acid solution at a solution temperature of 30° C. for 30 secondsto insolubilize a PVA layer comprised in the stretched laminate andcontaining oriented PVA molecules was performed. The insolubilizingaqueous boric acid solution in this step contained 3 weight parts ofboric acid with respect to 100 weight parts of water. The stretchedlaminate after the insolubilization step was dyed to form a dyedlaminate. This dyed laminate was obtained by immersing the stretchedlaminate in a dyeing solution to adsorb iodine to the PVA layercomprised in the stretched laminate. The dyeing solution containediodine and potassium iodide. A solution temperature of the dyeingsolution was set at 30° C., and an iodine concentration and a potassiumiodide were set, respectively, in the range of 0.08 to 0.25 weight % andin the range of 0.56 to 1.75 weight %, using water as a solvent. Aconcentration ratio of iodine to potassium iodide was set to 1:7. Asdyeing conditions, the iodine concentration and an immersion time wereset to allow a single transmittance of a PVA-based resin layerconstituting a polarizer to become 40.9%.

Subsequently, a step of immersing the dyed laminate in a cross-linkingaqueous boric acid solution at 30° C. for 60 minutes to subject PVAmolecules of the PVA layer having iodine adsorbed thereto to across-linking treatment. The cross-linking aqueous boric acid solutionin this cross-linking step contained 3 weight parts of boric acid withrespect to 100 weight parts of water, and 3 weight parts of potassiumiodide with respect to 100 weight parts of water. Then, the obtaineddyed laminate was further stretched in an aqueous boric acid solution ata stretching temperature of 70° C., in the same direction as that in theprevious in-air stretching, at a stretching ratio of 2.7 times to attainan ultimate total stretching ratio of 5.4 times, thereby obtaining anoptical film laminate comprising a polarizer for test sample. Theaqueous boric acid solution used in this stretching step contained 4.0weight parts of boric acid with respect to 100 weight parts of water,and 5 weight parts of potassium iodide with respect to 100 weight partsof water. The obtained optical film laminate was taken out from theaqueous boric acid solution, and boric acid adhering onto a surface ofthe PVA layer was washed away by an aqueous solution containing 4 weightparts of potassium iodide with respect to 100 weight parts of water. Thewashed optical film laminate was dried through a drying step using a hotair at 60° C. to obtain a 5 μm-thick polarizer laminated to the PETfilm.

[Production of Second Polarizer]

Except that the iodine concentration of the dyeing solution or bath andthe immersion time were changed to allow a PVA layer constituting afinally-formed polarizer to have a single transmittance of 42.8%, asecond polarizer was prepared in the same manner as that for the firstpolarizer.

[Production of Protective Layer]

Methacrylic resin pellets having a glutarimide ring unit were driedunder 100.5 kPa at 100° C. for 12 hours, and extruded from a T-die at adie temperature of 270° C. by using a single-screw extruder to form afilm. Then, this film was stretched in a conveyance direction thereof(hereinafter referred to as “the MD direction”) in an atmosphere at atemperature higher than a glass transition temperature Tg of the resinby 10° C., and further stretched in a direction perpendicular to the MDdirection (this direction will hereinafter be referred to as “the TDdirection”) in an atmosphere at a temperature higher than the glasstransition temperature Tg of the resin by 7° C., to obtain a 40 μm-thickacrylic-based protective film.

[Protective Film of First Polarizer]

An acrylic-based protective film with anti-reflection function (DSG 11produced by Dai Nippon Printing Co., Ltd., thickness: 47 μm) was used.

[Production Examples]

[Example of Production of First Retardation Layer]

(Production Example N-1)

A commercially-available polymer film consisting mainly of a cyclicpolyolefin-based polymer (produced by LSR Corporation, trade name “ARTONFILM FEKP 100 (thickness: 100 μm)”) was subjected to fixed-end uniaxialstretching using a tenter stretching machine, in a width direction (TDdirection) at 147° C., in such a manner as to have a film width 4.3times greater than its original film width (transverse stretching step).The obtained film had a thickness of 23 μm, and was a negative biaxialplate having a fast axis in the MD direction (nx>ny>nz).

(Production Example N-2)

A commercially-available polymer film consisting mainly of a cyclicpolyolefin-based polymer (produced by LSR Corporation, trade name “ARTONFILM FEKP 130 (thickness: 130 μm)”) was subjected to fixed-end uniaxialstretching using a tenter stretching machine, in a width direction at145° C., in such a manner as to have a film width 3.0 times greater thanits original film width (transverse stretching step). The obtained filmhad a thickness of 20 μm, and was a negative biaxial plate having a fastaxis in the MD direction (nx>ny>nz).

(Production Example N-3)

A composition obtained by melting and mixing a cyclic olefin-based resin(ZEONOR 1420R produced by ZEON Corporation) using a twin-screw meltextruder was extruded using a single-screw extruder having a T-dieattached thereto to obtain a 30 μm-thick cyclic olefin-based resin film.

The obtained film was subjected to fixed-end uniaxial stretching using atenter stretching machine, in a width direction at 145° C., in such amanner as to have a film width 4.3 times greater than its original filmwidth (transverse stretching step). The obtained film had a thickness of7 μm, and was a negative biaxial plate having a fast axis in the MDdirection (nx>ny>nz).

(Production Example N-4)

A commercially-available polymer film consisting mainly of a cyclicpolyolefin-based polymer (produced by LSR Corporation, trade name “ARTONFILM FEKP 100 (thickness: 130 μm)”) was subjected to fixed-end uniaxialstretching using a tenter stretching machine, in a width direction at147° C., in such a manner as to have a film width 3.4 times greater thanits original film width (transverse stretching step). The obtained filmhad a thickness of 38 μm, and was a negative biaxial plate having a fastaxis in the MD direction (nx>ny>nz).

[Example of Production of Second Retardation Layer]

(Synthesis of Fumarate-Based Resin)

48 g of hydroxypropyl methylcellulose (produced by Shin-Etsu ChemicalCo., Ltd., trade name: METOLOSE 60SH-50), 15601 g of distilled water,8161 g of fumaric acid diisopropyl ester, 240 g of methacrylic acid(3-ethyl-3-oxetanyl)methyl ester and 45 g of t-butyl peroxypivalateserving as a polymerization initiator were put in a 30-L autoclaveequipped with a stirrer, a cooling tube, a nitrogen inlet tube and athermometer. Subsequently, the mixture was subjected to nitrogenbubbling for one hour, and then held at 49° C. for 24 hours understirring at 200 rpm to induce radical suspension polymerization. Then,the solution was cooled to room temperature, and a suspension containingcreated polymer particles was centrifugally separated. The obtainedpolymer particles was washed twice by distilled water and twice bymethanol, and then dried under reduced pressure at 80° C. (yield: 80%).

(Production Example P-1)

The obtained fumarate-based resin was dissolved in a toluene-methylethyl ketone mixed solution (toluene/methyl ethyl ketone: 50 weight %/50weight %) to form a 20% solution thereof, and then 5 weight parts oftributyl trimellitate serving as a plasticizer was added with respect to100 weight parts of the fumarate-based resin. The obtained solution wascasted on a support substrate of a solution casting apparatus by a T-diemethod, and dried at 80° C. for 4 minutes and at 130° C. for 4 minutesto obtain a film having a width of 250 mm and a thickness of 18 μm. Theobtained film was subjected to free-end uniaxial stretching using a rollstretching machine, in the MD direction at 150° C. and at a stretchingratio of 1.04 times (longitudinal stretching step). The obtained filmhad a thickness of 18 μm, and was a positive biaxial plate having a fastaxis in the MD direction (nz>nx>ny).

(Synthesis of Poly(Nitrostyrene))

A solvent-based mixture of nitrobenzene (900 g) and 1,2-dichloroethane(300 g) was put in a three-neck round-bottom flask equipped with amechanical stirrer, and polystyrene (50.0 g) was dissolved in themixture under stirring. An acid mixture consisting of nitric acid (86.0g) and concentrated sulfuric acid (100.0 g) (nitro/styrene equivalentratio=2/1) was dripped into and added to the stirred mixture for 30minutes. The obtained mixture was subjected to reaction under nitrogenat room temperature for a total time of 22 hours. The resulting yellowmixture was poured into sodium hydroxide diluted with water to separatean organic layer, and then the organic layer was precipitated inmethanol to provide a piece of solid substance. The solid was solved inN,N-dimethylformamide (DMF), and re-precipitated in methanol. Theobtained precipitate was subjected to stirring for 2 hours, filtering,repetitive washing with methanol, and drying under vacuum to obtain aslightly yellowish fibrous powder. A yield was 95% or more in total.

(Production Example P-2)

The obtained poly(nitrostyrene)-based resin was dissolved incyclopentanone to form a 20% solution thereof, and the solution wascasted on a support substrate of a solution casting apparatus by a T-diemethod. Then, the cast solution was dried at 40° C. for 4 minutes and at130° C. for 4 minutes, and further dried under vacuum to obtain a filmhaving a width of 250 mm and a thickness of 3 μm. The obtained film wassubjected to free-end uniaxial stretching using a roll stretchingmachine, in the MD direction at 184° C. and at a stretching ratio of1.06 times (longitudinal stretching step). The obtained film had athickness of 3 μm, and was a positive biaxial plate having a fast axisin the MD direction (nz>nx>ny).

(Production Example P-3)

A pellet-shaped resin of polystyrene resin (“XAREC 130ZC” produced byIdemitsu Kosan Co., Ltd.) was extruded at 290° C. using a single-screwextruder and a T-die, and a resulting sheet-shaped molten resin wascooled by a cooling drum to obtain a 20 μm-thick film. This film wassubjected to free-end uniaxial stretching using a roll stretchingmachine, in the MD direction at 125° C. and at a stretching ratio of 1.5times to obtain a retardation film having a fast axis in the MDdirection (longitudinal stretching step). The obtained film was furthersubjected to fixed-end uniaxial stretching using a tenter stretchingmachine, in a width direction at 130° C., in such a manner as to have afilm width 1.6 times greater than a film width just after the abovelongitudinal stretching, thereby obtaining a 10 μm-thickbiaxially-stretched film (transverse stretching step). The obtained filmwas a positive biaxial plate having a fast axis in the MD direction(nz>nx>ny).

(Production Example P-4)

A pellet-shaped resin of styrene-maleic anhydride polymer (“DYLARK D232”produced by NOVA Chemicals Japan Ltd.) was extruded at 270° C. using asingle-screw extruder and a T-die, and a resulting sheet-shaped moltenresin was cooled by a cooling drum to obtain a 77 μm-thick film. Thisfilm was subjected to free-end uniaxial stretching using a rollstretching machine, in the MD direction at 125° C. and at a stretchingratio of 1.7 times to obtain a retardation film having a fast axis inthe MD direction (longitudinal stretching step). The obtained film wasfurther subjected to fixed-end uniaxial stretching using a tenterstretching machine, in a width direction at 135° C., in such a manner asto have a film width 1.8 times greater than a film width just after theabove longitudinal stretching, thereby obtaining a 33 μm-thickbiaxially-stretched film (transverse stretching step). The obtained filmwas a positive biaxial plate having a fast axis in the MD direction(nz>nx>ny).

[Production of Laminate Consisting of First Polarizer, First RetardationLayer, Second Retardation Layer and Protective Layer]

The first retardation layer N-1 prepared in the above manner waslaminated to the 5 μm-thick polarizer comprised in the laminate preparedin the example of production of the first polarizer, specifically, to asurface of the 5 μm-thick polarizer on a side opposite to the PET filmof the laminate, through a UV-curable adhesive. Subsequently, after thePET film was peeled from the laminate, the acrylic-based protective filmwith anti-reflection function was laminated to the polarizer through aUV-curable adhesive. Then, the second retardation layer P-1 was furtherlaminated to a surface of the resulting laminate on the side of thefirst retardation layer N-1, through an acrylic-based pressure-sensitiveadhesive (thickness: 5 μm), in a roll-to-roll manner, i.e., under acondition that they are conveyed parallel to each other, therebyobtaining a first polarizing laminate.

[Production of Laminate Consisting of Second Polarizer and ProtectiveFilm]

The 40 μm-thick acrylic-based protective film was laminated to the 5μm-thick polarizer comprised in the laminate prepared in the example ofproduction of the second polarizer, specifically, to a surface of the 5μm-thick polarizer on a side opposite to the PET film of the laminate,through a UV-curable adhesive. Subsequently, the PET film was peeledfrom the laminate to obtain a second polarizing plate (second polarizinglaminate) laminated to the acrylic-based protective film.

Production of Liquid Crystal Panel Example 1

From a slate type PC equipped with an IPS type liquid crystal cell (iPadRetina Display Model produced by Apple Inc.), the liquid crystal cellwas taken out, and polarizing plates disposed on the top and bottomsides of the liquid crystal cell were removed. Then, opposite glasssurfaces of the liquid crystal cell were cleaned by washing.Subsequently, the first polarizing plate produced in the above mannerwas laminated to the viewing-side surface of the liquid crystal cellwith the absorption axis of the polarizer of the first polarizinglaminate oriented in a direction perpendicular to the initialorientation direction of the liquid crystal cell, through anacrylic-based pressure-sensitive adhesive (thickness: 15 μm). Then, thesecond polarizing plate produced in the above manner was laminated tothe illumination light source-side surface of the liquid crystal cellwith the absorption axis of the polarizer of the second polarizinglaminate oriented in a direction parallel to the initial orientationdirection of the liquid crystal cell, through an acrylic-basedpressure-sensitive adhesive (thickness: 15 μm).

Examples 2 to 3

In the example of production of a first polarizing plate, two differenttypes of first polarizing plates were obtained using: the firstretardation layer N-2 and the second retardation film P-2; and the firstretardation layer N-3 and the second retardation film P-3, instead ofthe first retardation layer N-1 and the second retardation film P-1.Then, a liquid crystal panel was produced in the same manner as that inExample 1, using each of the obtained first polarizing plates.

Example 4

Except that, in the example of production of a first polarizing plate,each of the first retardation layer N-1 and the second retardation filmP-1 was laminated through a light-curable adhesive (storage elasticmodulus: 2.6×10⁶, thickness: 2 μm), a liquid crystal panel was producedin the same manner as that in Example 1.

Example 5

Except that, in the example of production of a first polarizing plate,each of the first retardation layer N-2 and the second retardation filmP-2 was laminated through a light-curable adhesive (storage elasticmodulus: 4.0×10⁵, thickness: 2 μm), a liquid crystal panel was producedin the same manner as that in Example 1.

Example 6

Except that, in the example of production of a first polarizing plate,each of the first retardation layer N-3 and the second retardation filmP-3 was laminated through a light-curable adhesive (storage elasticmodulus: 9.0×10⁷, thickness: 2 μm), a liquid crystal panel was producedin the same manner as that in Example 1.

[Black-State Brightness]

A block image was displayed on a liquid crystal display device in a darkroom at a room temperature of 23°, brightness (Y value in an XYZ colorcoordinate system) was measured using “EZContrast 160D (product name)”produced by ELDIM SA, and an average of black-state brightness in anazimuth range of 0 to 360° at a polar angle of 60° was calculated. Aresult of the calculation is presented in Table 2. In Table 2, the term“polar angle” means an inclination angle with respect to a normal lineperpendicular to a screen of the liquid crystal display device, and theterm “azimuth” means a counterclockwise angle with respect to adirection corresponding to three o'clock of a clock dial when viewingthe screen from a front side thereof.

TABLE 2 Average First retardation layer of black- Negative B plate statemoisture bright- Mate- Thick- perme- ness rial ness Δnxy Δnxz ability(cd/cm²) Example 1 N-1 23 0.0048 0.0052 85 0.73 Example 2 N-2 20 0.00680.0095 98 0.74 Example 3 N-3 7 0.0129 0.0206 60 0.75 Comparative N-4 380.0033 0.0039 78 0.75 Exampke 1 Average of black- Second retardationlayer state Positive B plate bright- Mate- Thick- ness rial ness ΔnxyΔnxz (cd/cm²) Example 1 P-1 18 0.0014 −0.0043 0.73 Example 2 P-2 30.0050 −0.0217 0.74 Example 3 P-3 10 0.0045 −0.0067 0.75 Comparative P-433 0.0007 −0.0026 0.75 Example 1

In Examples, the iPad having a brightness-enhancing film was used as aliquid crystal panel for evaluation. Thus, as regards Examples in thePatent Document 3 using a TV panel as a liquid crystal panel,black-state brightness values in the above Table 2 are higher than thosepresented in Table 3 of the Patent Document 3. However, such black-statebrightness values in the above Table 2 are at a sufficientlysatisfactory level. The result also shows that the present invention canachieve a totally satisfying compensation effect, despite a reduction inthickness of the retardation layers. Each of the retardation layers inExamples (Inventive Examples) 1 to 3 has a thickness less than that ofComparative Example 1, and exhibits a black-state value less than, or,even at worst, equal to that of Comparative Example 1.

[Thickness of Polarizing Laminate]

The polarizing laminate comprising the protective layer, the polarizer,the first retardation layer and the second retardation layer which arelaminated together was measured in thickness using a digital micrometer(KC-351C produced by Anritsu Corporation).

TABLE 3 First Second Thickness of Retardation RetardationPressure-sensitive Polarizing Layer Layer adhesive/Adhesive plateMaterial Material Material Thickness (laminate) Example 1 N-1 P-1Acrylic-based 5 113 pressure-sensitive adhesive Example 2 N-2 P-2Acrylic-based 5 95 pressure-sensitive adhesive Example 3 N-3 P-3Acrylic-based 5 89 pressure-sensitive adhesive Example 4 N-1 P-1Light-curable adhesive 2 110 Example 5 N-2 P-2 Light-curable adhesive 292 Example 6 N-3 P-3 Light-curable adhesive 2 86 Comparative N-4 P-4Acrylic-based 5 143 Example 1 pressure-sensitive adhesive

It has been verified that the polarizing laminate comprising the firstretardation layer and the second retardation layer each laminated usinga light-curable adhesive can achieve thickness reduction.

LIST OF REFERENCE SIGNS

-   1: liquid crystal panel-   10: liquid crystal cell-   11: first polarizer-   12: first retardation layer-   13: second retardation layer-   14, 15: pressure-sensitive adhesive layer-   16: protective layer-   17: anti-reflection layer-   21: second polarizer-   22, 24: pressure-sensitive adhesive layer-   23: protective layer-   25: brightness-enhancing film

1. A liquid crystal panel comprising: a liquid crystal cell having aliquid crystal layer containing liquid crystal molecules oriented in onedirection in a plane thereof in an electric field-off state; a firstpolarizer disposed on a side of the liquid crystal cell; a secondpolarizer disposed on a side of the liquid crystal cell opposite to theside of the liquid crystal cell having the first polarizer, the secondpolarizer having an absorption axis that orthogonally intersects anabsorption axis of the first polarizer; and a first retardation layerand a second retardation layer between the first polarizer and theliquid crystal cell and arranged in this order from a side of the firstpolarizer, wherein the second retardation layer is laminated to thefirst retardation layer through a light-sensitive adhesive having astorage elastic modulus of 3×105 to 1×108 Pa (25° C.).
 2. The liquidcrystal panel of claim 1, wherein the first retardation layer isconfigured to satisfy the relationship of nx1>ny1>nz1, where: nx1represents a refractive index in an in-plane slow axis direction, ny1represents a refractive index in an in-plane fast axis direction, andnz1 represents a refractive index in a thickness-wise direction, and thesecond retardation layer is configured to satisfy the relationship ofnz2>nx2>ny2, where nx2 represents a refractive index in the in-planeslow axis direction, ny2 represents a refractive index in the in-planefast axis direction, and nz2 represents a refractive index in thethickness-wise direction, the slow axis of the first retardation layeris parallel to the slow axis of the second retardation layer.
 3. Theliquid crystal panel of claim 2, wherein the first retardation layer hasa thickness of 25 μm or less, and a moisture permeability of 200 g/m2 orless, wherein a value of Δnxy1 and a value of Δnxz1 are, respectively,0.0036 or more, and 0.0041 or more, and Re and Rth are, respectively, inthe range of 90 nm to 140 nm and the range of 100 nm to 240 nm, whereΔnxy1 represents a difference between the refractive index nx1 in theslow axis direction and the refractive index ny1 in the fast axisdirection, Δnxz1 represents a difference between the refractive indexnx1 in the slow axis direction and the refractive index nz1 in thethickness direction, Re represents an in-plane retardation, and Rthrepresents a thicknesswise retardation expressed in the formulaRth=(nx1−nz1)×d1, where d1 represents a thickness of the firstretardation layer, and the second retardation layer has a thickness of20 μm or less, wherein a value of ×nxy2 and a value of Δnxz2 are,respectively, 0.0008 or more, and −0.0030 or less, and Re and Rth are,respectively, in the range of 15 nm to 50 nm and the range of −110 nm to−60 nm, where ×nxy2 represents a difference between the refractive indexnx2 in the slow axis direction and the refractive index ny2 in the fastaxis direction, Δnxz2 represents a difference between the refractiveindex nx2 in the slow axis direction and the refractive index nz2 in thethickness direction, Re represents an in-plane retardation, and Rthrepresents a thicknesswise retardation expressed in the formulaRth=(nx2−nz2)×d2, where d2 represents a thickness of the secondretardation layer.
 4. The liquid crystal panel of claim 3, wherein thethickness of the first retardation layer is greater than the thicknessof the second retardation layer.
 5. The liquid crystal panel of claim 1,wherein each of the first polarizer and the second polarizer have athickness of 10 μm or less, with optical properties including a singletransmittance of 40.0% or more and a polarization degree of 99.8% ormore.
 6. The liquid crystal panel of claim 1, wherein the secondpolarizer is directly bonded to the liquid crystal cell through apressure-sensitive adhesive layer with the absorption axis thereof beingparallel to an orientation direction of the liquid crystal molecules ofthe liquid crystal cell in the electric field-off state.
 7. The liquidcrystal panel of claim 1, wherein the second polarizer has a firstprotective layer laminated thereto at a side opposite to the liquidcrystal cell, through a pressure-sensitive adhesive layer.
 8. The liquidcrystal panel of claim 7, wherein the first protective layer has athickness of 10 to 50 μm, and a moisture permeability of 200 g/m2 orless.
 9. The liquid crystal panel of claim 7, wherein the firstpolarizer has a second protective layer laminated thereto at a sideopposite to the first retardation layer.
 10. The liquid crystal panel ofclaim 9, wherein the second protective layer has a thickness of 50 μm orless and a moisture permeability of 200 g/m2 or less.
 11. A liquidcrystal panel comprising: a liquid crystal cell having a liquid crystallayer containing liquid crystal molecules oriented in one direction in aplane thereof in an electric field-off state; a first polarizer disposedon a side of the liquid crystal cell; a second polarizer disposed on aside of the liquid crystal cell opposite to the side of the liquidcrystal cell having the first polarizer, the second polarizer having anabsorption axis that orthogonally intersects an absorption axis of thefirst polarizer; and a first retardation layer and a second retardationlayer between the first polarizer and the liquid crystal cell andarranged in this order from a side of the first polarizer, wherein thesecond retardation layer is laminated to the first retardation layerthrough a light-sensitive adhesive having a storage elastic modulus of3×105 to 1×108 Pa (25° C.), and the second polarizer is bonded to theliquid crystal cell.
 12. The liquid crystal panel of claim 11, whereinthe first retardation layer is configured to satisfy the relationship ofnx1>ny1>nz1, where: nx1 represents a refractive index in an in-planeslow axis direction, ny1 represents a refractive index in an in-planefast axis direction, and nz1 represents a refractive index in athickness-wise direction, and the second retardation layer is configuredto satisfy the relationship of nz2>nx2>ny2, where nx2 represents arefractive index in the in-plane slow axis direction, ny2 represents arefractive index in the in-plane fast axis direction, and nz2 representsa refractive index in the thickness-wise direction, the slow axis of thefirst retardation layer is parallel to the slow axis of the secondretardation layer.
 13. The liquid crystal panel of claim 12, wherein thefirst retardation layer has a thickness of 25 μm or less, and a moisturepermeability of 200 g/m2 or less, wherein a value of Δnxy1 and a valueof Δnxz1 are, respectively, 0.0036 or more, and 0.0041 or more, and Reand Rth are, respectively, in the range of 90 nm to 140 nm and the rangeof 100 nm to 240 nm, where Δnxy1 represents a difference between therefractive index nx1 in the slow axis direction and the refractive indexny1 in the fast axis direction, Δnxz1 represents a difference betweenthe refractive index nx1 in the slow axis direction and the refractiveindex nz1 in the thickness direction, Re represents an in-planeretardation, and Rth represents a thicknesswise retardation expressed inthe formula Rth=(nx1−nz1)×d1, where d1 represents a thickness of thefirst retardation layer, and the second retardation layer has athickness of 20 μm or less, wherein a value of ×nxy2 and a value ofΔnxz2 are, respectively, 0.0008 or more, and −0.0030 or less, and Re andRth are, respectively, in the range of 15 nm to 50 nm and the range of−110 nm to −60 nm, where ×nxy2 represents a difference between therefractive index nx2 in the slow axis direction and the refractive indexny2 in the fast axis direction, Δnxz2 represents a difference betweenthe refractive index nx2 in the slow axis direction and the refractiveindex nz2 in the thickness direction, Re represents an in-planeretardation, and Rth represents a thicknesswise retardation expressed inthe formula Rth=(nx2−nz2)×d2, where d2 represents a thickness of thesecond retardation layer,
 14. The liquid crystal panel of claim 11,wherein at least one of the first polarizer or the second polarizer hasa thickness of 10 μm or less, with optical properties including a singletransmittance of 40.0% or more and a polarization degree of 99.8% ormore.
 15. The liquid crystal panel of claim 11, wherein the secondpolarizer is directly bonded to the liquid crystal cell through apressure-sensitive adhesive layer.
 16. The liquid crystal panel of claim11, wherein the absorption axis of the second polarizer is parallel toan orientation direction of the liquid crystal molecules of the liquidcrystal cell in the electric field-off state.
 17. The liquid crystalpanel of claim 11, wherein the second polarizer has a first protectivelayer laminated thereto at a side opposite to the liquid crystal cell,and the first polarizer has a second protective layer laminated theretoat a side opposite to the first retardation layer.
 18. The liquidcrystal panel of claim 17, wherein the first protective layer has athickness of 10 to 50 μm, and a moisture permeability of 200 g/m2 orless.
 19. The liquid crystal panel of claim 17, wherein the secondprotective layer has a thickness of 50 μm or less and a moisturepermeability of 200 g/m2 or less.
 20. The liquid crystal panel of claim11, wherein the first retardation layer is thicker than the secondretardation layer.